Multigeometry nanoparticle and multicompartment superstructure construction with block copolymers: Molecular design, solution assembly, and kinetics.

摘要

Compositional and geometrical complexity of nano-sized objects has long been an important topic in materials science leading to novel properties and applications. In fields such as nano-medicine, organic photonics and electronics, this typically involves novel polymeric nano-assemblies and their templated hybrid materials.;Multigeometry nanoparticles, due to segregation of unlike-shaped block copolymer molecules trapped within the same micelle structures, have been produced via assembly of block copolymer mixtures in tetrahydrofuran/water solution. The mixture is composed of two block copolymers with distinctive hydrophobic blocks but the same poly(acrylic acid) (PAA) hydrophilic block. By taking advantage of the complexation in the hydrophilic corona between the acid side chains of the PAA block and added organoamine molecules, unlike hydrophobic blocks can be trapped in the same micelle core. Locally, the unlike hydrophobic blocks can segregate into compartments and even express different interfacial curvatures, or geometries, within the same nanoparticle. Through controlled kinetic pathways, block copolymer design and mixing ratios, both micelle compartment size and shape can be controlled to construct a novel class of multigeometry nanoparticles from molecular geometric blends of sphere-sphere, sphere-cylinder, cylinder-cylinder, cylinder-bilayer, or sphere-bilayer.;Furthermore, hierarchical superstructures have been built up from pre-assembled block copolymer nanoparticles by taking advantage of their compositional/geometrical anisotropy and the controlled inter-particle association due to post-polymerization chemical modification. New block copolymer mixture using crown ether grafted block copolymers produced dynamic, complex sphere nanoparticle with inter-particle association properties in the presence of diamine molecules due to ammonium-crown ether supramolecular interactions, resulting in one-dimensional, two-dimensional and three-dimensional arrays of particles in dilute solution. These superstructures are dynamic internally, morphologically evolve into multicompartment superstructures with well-defined subdomains, and are capable to disassemble subsequently into novel multicompartment nanoparticles. Another new block copolymer mixture using hydroxyethyl acrylate grafted block copolymers produce sphere-sphere multigeometry nanoparticles with anisotropic distribution of carbon-carbon double bonds on the particle surface. UV crosslinking of the particle solution gives rise to particle dimers and other multicompartment cluster formations.